Class A-B amplifiers ensure accurate amplification through the balance of non-saturated sink and source (push-pull) output stage sections which each provide current of a single polarity through both polarities of the output.
Class D amplifiers yield higher efficiency than class A-B amplifiers, through use of saturated mutually-exclusive sink and source switching devices. Being reliant on such devices, however, this class of amplifier enjoys no balancing mechanism. In that current in the output stage of a class D amplifier is not always in phase with the voltage, bulk devices which can conduct current in two directions, such as MOSFETs, are thus used to ensure that higher-potential devices may sink current, and that lower-potential devices may source current. MOSFETs, however, are more expensive than their bipolar counterparts, which conduct current only in a single direction.
The need exists for a circuit configuration and a method whereby less-expensive bipolar switching devices may be employed in high-accuracy class D amplifiers.